In the field of medication delivery devices including so-called “syringe pumps,” typically a pre-filled medication syringe is mechanically driven under microprocessor control to deliver a prescribed amount or dose of a fluid at a controlled rate to a patient through an infusion line fluidly connected to the syringe. Syringe pumps typically include a motor that rotates a leadscrew. The leadscrew in turn activates a plunger driver which forwardly pushes a plunger within a barrel of the syringe. Pushing the plunger forward thus forces the dose of medication outwardly from the syringe, into the infusion line, and to the patient—typically, intravenously. Examples of syringe pumps are disclosed in U.S. Pat. No. 4,978,335 titled “Infusion Pump with Bar Code Input to Computer,” U.S. Pat. No. 8,182,461 titled “Syringe Pump Rapid Occlusion Detection System,” and U.S. Pat. No. 8,209,060 titled “Updating Syringe Profiles for a Syringe Pump.” As used throughout this disclosure, the term “syringe pump” is intended to generally pertain to any device which acts on a syringe to controllably force fluid outwardly therefrom.
Syringe pumps are used to control the delivery of drugs or fluids to a patient that include, but are not limited to: therapeutic agents; nutrients; drugs; medicaments such as antibiotics, blood clotting agents, and analgesics; and other fluids. The devices can be used to introduce the drugs or fluids into patients' bodies utilizing any of several routes such as, for example, intravenously, subcutaneously, arterially, or epidurally.
In use of syringe pumps it may be desirable, or even required in particular circumstances, to characterize a particular syringe that is installed in a particular device, for determination or prediction of an amount of fluid that will be forced outwardly from the syringe per linear unit travel of the plunger. Commonly, syringes are characterized by manufacturers of syringes and/or syringe pumps according to pre-determined criteria, such as outer diameters. This characterization data may be electronically stored in a syringe database loaded into a syringe pump. Thus, determination of an outer diameter of a particular syringe may primarily serve a purpose of limiting or filtering a list of possible syringes from the pump database which have outer diameters that approximate an outer diameter of the particular syringe. However, various means and methods have also been proposed for characterization of syringes while installed in syringe pumps. These known means and methods of characterization, however, have often merely focused on determinations of outer diameters of syringe barrels by way of moveable measurement jaws, clamps, and the like provided on or in the pumps. Other known means and methods have employed conventional rulers or other linearly ruled components coupled to the pumps, with or without such syringe barrel outer diameter sensors. These rudimentary ruled components have typically been provided in substantially parallel orientations along central longitudinal axes of syringes installed in the pumps. In use of such a ruled device, a health care practitioner would, for example, visually inspect the length of the syringe with respect to the ruled component for visually determining a volume or “length” of fluid contained within the syringe, a location of a tip of the plunger within the syringe, a distance of maximum possible linear travel of the plunger tip with the syringe barrel, and/or any other desired parameters. The user would then typically compare such metrics to a list or database of similar parameters of known syringe types, sizes, and brands, etc. However, such ad hoc visual inspection is prone to errors that may arise from, for example, a lack of adequate visual acuity of the user and variability in interpretation and definition of the parameters. Thus, such known devices and methods have not been entirely satisfactory for syringe characterization—and some such devices and methods have even been deemed to be unsafe and unfit for human use. Furthermore, characterization of “unknown” syringes may be problematic or even impossible within an acceptable degree of reliability, accuracy, and repeatability. In this context, “unknown” refers to those syringes that have not been previously characterized or those that are not listed in, for example, an aforementioned database or look-up table.
It would therefore be useful and advantageous to provide devices and methods which provide some degree of reliability, accuracy, and repeatability in syringe characterization, particularly with respect to unknown syringes.